The p-Phthalates Terephthalic Acid and Dimethyl Terephthalate Used in the Manufacture of PET Induce In Vitro Adipocytes Dysfunction by Altering Adipogenesis and Thermogenesis Mechanisms

Public health concerns associated with the potential leaching of substances from Polyethylene terephthalate (PET) packaging have been raised due to the role of phthalates as endocrine-disrupting chemicals or obesogens. In particular, changes in the environment such as pH, temperature, and irradiation can improve contaminant migration from PET food packaging. In this study, the in vitro effects of p-phthalates terephthalic acid (TPA) and dimethyl terephthalate (DMT) on murine adipocytes (3T3-L1) were evaluated using concentrations that might be obtained in adult humans exposed to contaminated sources. TPA and, in particular, DMT exposure during 3T3-L1 differentiation increased the cellular lipid content and induced adipogenic markers PPAR-γ, C/EBPß, FABP4, and FASN, starting from low nanomolar concentrations. Interestingly, the adipogenic action of TPA- and DMT-induced PPAR-γ was reverted by ICI 182,780, a specific antagonist of the estrogen receptor. Furthermore, TPA and DMT affected adipocytes’ thermogenic program, reducing pAMPK and PGC-1α levels, and induced the NF-κB proinflammatory pathway. Given the observed effects of biologically relevant chronic concentrations of these p-phthalates and taking into account humans’ close and constant contact with plastics, it seems appropriate that ascertaining safe levels of TPA and DMT exposure is considered a high priority.